1. Field of the Invention
The present invention relates to a bio-information detecting sensor, and more particularly, to a bio-information detecting sensor capable of measuring heartbeat and oxygen saturation in blood.
2. Discussion of Related Art
Generally, in a medical institution or general household, bio-information detecting sensors for detecting heart rates, respiration, other bio-activities, and the like are used.
For example, there is a heartbeat and oxygen saturation sensor capable of measuring oxygen saturation in blood using light absorption of hemoglobin. The heartbeat and oxygen saturation sensor using optical elements can relatively simply noninvasively detect bio-information.
A conventional heartbeat and oxygen saturation sensor using an optical element can be divided into a transmission type sensor or a reflection type sensor according to a type thereof.
In the transmission type sensor, a bio-medium (such as a finger or earlobe) is placed between a light emitting diode (LED) and a photodiode (PD), and light emitted from the LED passes through the bio-medium and is received by the PD so that bio-information is obtained.
In the reflection type sensor, an LED is disposed to be coplanar with a PD, the LED emits light to a bio-medium, and the PD receives the light reflected by the bio-medium so that biomedical information is obtained.
Light passing through a bio-medium tends to be distributed more widely than an incident angle of the emitted light due to a scattering effect inside the bio-medium, and since degrees of absorption and scattering vary according to a wavelength of the emitted light, a difference in light distribution in which the light is concentrated tends to occur.
Conventional transmission and reflection type heartbeat and oxygen saturation sensors are generally formed by arranging optical elements based on silicon or III-V compound semiconductors. Such conventional inorganic semiconductor-based optical elements have difficulty in securing mechanical flexibility and stretchability, and thus are limited in application to various parts of a body. In addition, a spatial arrangement of light emitting elements and light receiving elements should be optimized to efficiently receive light, but the conventional inorganic semiconductor-based optical elements are mainly formed in a rectangular shape, and thus are very limited in design freedom for obtaining high efficiency signals. Since a wearable health care sensor capable of monitoring at all times requires small power consumption of a light source for securing a sufficient signal, the limit of design freedom of a present technology can be a serious problem in reduction of the power consumption.